Orthogonal frequency-division multiple-access (OFDMA) has emerged as a promising multiple-access technique for next-generation wireless networks operating over wideband multi-path fading channels. Classical OFDMA, which involves assigning orthogonal (non-overlapping) subcarriers among different users, is an effective means to handle multi-path fading with low-complexity receivers and to obtain multi-user diversity gains via channel-dependent frequency-domain scheduling. Consequently, resource allocation for classical single-cell OFDMA systems has been the subject of intense research in recent years. The methods designed for single-cell OFDMA systems are directly applicable to a multi-cell OFDMA system employing static frequency reuse wherein inter-cell interference is avoided by ensuring adjacent cells are allocated orthogonal frequency bands. This allows for autonomous resource allocation at each base-station at the expense of reduced system throughput. The resource allocation problems for OFDMA systems are in general non-linear and non-convex which has prompted several heuristic approaches. It is also known that many OFDMA resource allocation problems satisfy a time sharing property in the limit of large number of subcarriers and hence in principle optimal solutions can be obtained via dual decomposition techniques. Unfortunately, the complexities of the dual decomposition technique as well as many heuristic algorithms are still too high for most practical cellular systems being considered for deployment.
Future wireless network evolutions are envisioned to employ a full (or an aggressive) frequency reuse. However, co-channel interference caused by transmissions in neighboring cells will be a major impairment that limits throughput. Consequently, proactive inter-cell interference mitigation techniques are required. Joint resource allocation over a cluster of neighboring cells via base-station coordination is a promising solution. However, most recent works focused on downlink systems and the design of distributed uplink resource allocation algorithms that require limited information exchange among base-stations is still in its infancy.